It doesn't look like damage from stress on the frame. There's no evidence of cracking or stretching or anything that would indicate stress. It looks more like impact damage from a mechanical part, as there are multiple sets of holes equally spaced.The bikes were transported on a rack and was fine when we got there.
I noticed it after a ride and couldn't figure out what happened. My best guess was stress on the frame from riding.
Could be, I don't have the expertise to say. Is it possible those marks were there before, but you just hadn't noticed them? Either way, probably worth a call to whomever you bought it from.Someone else has suggested its from the frame being contaminated during the powder coating process, bubbles formed and I guess then popped. Seems to make sense.